DESCRIPTION (Applicant's abstract): While depression is a leading cause of work disability in this nation, disability reduction efforts remain hampered by a lack of research. This study's long-term goal is to prevent work disability due to depression. A longitudinal study is proposed that addresses on-the-job work disability among employed primary care patients with depression. The sample will include 350 patients who have Major Depressive Disorder (MDD) and/or dysthymia and are employed at baseline, and two comparison groups: 1)) 200 workers with rheumatoid arthritis (PA), a physically limiting condition with one of the highest work disability rates; and 2) 100 "healthy" controls. The study has 3 specific aims: 1) to prospectively assess and compare the rates at which four types of work disabilities (job loss, work time loss, reduced work hours and on-the-job limitations) occur among the groups; 2) to identify variables that contribute to successful and unsuccessful work outcomes among patients with depression; 3) to determine whether the variables that contribute to work disability are the same for depression and RA. The project's health-relatedness is its focus on a major public health problem (work disability due to depression) within an increasingly important segment of the mental health care delivery system (primary care). Subjects will be recruited from primary care practices, 18-62 years of age, employed at baseline and not planning to stop working for at least 2 years. Data will be collected from patient surveys (baseline and months 3, 6, 12 and 18), patient charts and clinic pharmacy records. We will also administer a new validated survey instrument; The Work Limitations Questionnaire, which assesses on-the-job performance and productivity and, thus, captures aspects of work disability not reflected in job loss and absenteeism data. The statistical analysis will: 1) establish the magnitude of the four types of work disability and work productivity costs within the depression sample); 2) identify variables that predict work disability or a sustained ability to work; and 3) determine the differential impact of a mental and a physical illness on work disability rates, the predictors of work disability and productivity costs. Study results will contribute to the design of disability prevention and productivity improvement programs and policies.